Search

A new kinetic-magnetohydrodynamic hybrid simulation model where the gyrokinetic particle-in-cell simulation is applied to both thermal ions and energetic particles is presented. Toroidal Alfvén eigenmodes (TAEs) destabilized by energetic ions in tokamak plasmas are simulated with the new simulation model. Energy channeling from energetic ions to thermal ions through Alfvén eigenmodes (AEs) is demonstrated by the simulation. The distribution function fluctuations and the resonance condition are analyzed for both thermal ions and energetic ions. The strong energy transfer between the particles and the AE and the strong particle transport occur when the following conditions are satisfied at the resonance location in phase space: (1) the poloidal resonance number is close to the poloidal mode number of the AE, (2) the AE has a substantial amplitude, (3) the distribution function has a substantial gradient along the E ′ = const. line, where E ′ is a conserved variable for the wave-particle interaction. While the distribution function fluctuations for energetic ions are consistent with the resonance condition with the TAEs, the distribution function fluctuations for thermal ions do not satisfy the resonance condition when the bulk plasma beta is 1%. This indicates that the resonance does not play an important role in the interaction between thermal ions and the TAE for the relatively low bulk plasma temperature. On the other hand, when the bulk plasma beta is 4%, the resonance between thermal ions and the TAEs become important leading to Landau damping.

Ion temperature gradient (ITG) driven turbulence is investigated by means of gyrokinetic simulations which include both kinetic ions and electrons in slab geometry with uniform equilibrium magnetic field. The study confirms that numerical results satisfy the entropy balance equation including both ions and electrons. The entropy variable is transferred from ions to electrons through the perturbation of electrostatic potential, and the transferred fluctuation is diffused by the electron collision dissipation. In the ITG turbulence with kinetic electrons ion heat diffusion is larger than that with adiabatic electrons. The former is close to the latter when the ion mass is comparable to or larger than the hydrogen one. The difference between the transport coefficients does not originate from the suppression of turbulence by zonal flow, but stems from the difference between their spectra. The lowest wavenumber mode dominates the coefficient in the adiabatic electron case, while the transport is caused not only by the the lowest mode but by higher wavenumbers in the kinetic electron cases.